Preparation of ketones

ABSTRACT

Disclosed is a method for the preparation of ketones by a catalytic vapor phase reaction of using reactants such as ketones with carboxylic acids and/or carboxylic acid precursors. An example of such a reaction is that of acetone with pivalic acid over a ceria-alumina catalyst at a temperature of nearly 470° C. to produce pinacolone.

BACKGROUND OF THE INVENTION

This application is a continuation-in-part of copending U.S. applicationSer. No. 159,309, filed June 9, 1980, now abandoned which priorapplication was in turn a continuation of prior application Ser. No.876,334, filed Feb. 9, 1978, now abandoned, which was a continuation oforiginal application Ser. No. 716,142, filed Aug. 20, 1976, nowabandoned.

The present invention relates generally to a method for preparingketones using reactants such as ketones and carboxylic acids. In oneembodiment, it relates to an entirely new process for the production ofunsymmetrical ketones from ketones and carboxylic acids over aceria-alumina catalyst system in the temperature range of 300° to 550°C. utilizing a very short contact time over the catalyst to achieve aconversion in the range of 85 percent or more while recovering most ofthe unconverted reactants for recycling. An excellent example of such areaction is the reaction of acetone with pivalic acid over aceria-alumina catalyst to produce pinacolone.

Pinacolone is an intermediate which is useful in the preparation ofpharmaceutical products and pesticides for which improved methods ofmanufacture have been sought for some time now. An electrolyticreductive coupling of acetone to form pinacol which can be converted topinacolone has been carried out on an experimental basis for a number ofyears to produce small quantities of pinacol, but such processes havethus far failed to receive much commercial utilization because of thecost factors involved in these methods.

A thermo-chemical route as taught by literature utilizes a pyrolysis ofone or two carboxylic acids to yield symmetrical or unsymmetricalketones, respectively. This type of reaction has been used commerciallywith the significant disadvantage that the raw materials used in themanufacture of the ketones are costly because the selectivity of thereaction to unsymmetrical ketones is low.

The article Thermal Behavior of Aliphatic and Alicyclic Ketones, J.Chem. Soc. Japan, Vol. 87, No. 10 (1966) pp. 1108-1110 by Furukawa andNaruchi describes observations of work done in the study of the thermaldecomposition of ketones. In the course of this work, ketones werereacted together at 500° C. in the presence of calcium carbonate. Theauthors do not show the production of ketones from a ketone and acarboxylic acid or carboxylic acid precursor nor do they show anyrecycle features. This article may tend to indicate the possibility of"equilibrating" two symmetric ketones to form an unsymmetrical ketoneand the possibility of "equilibrating" an unsymmetric ketone to twodifferent symmetric ketone, but the discussion on p. 10 (Englishtranslation) indicates that this is not the case.

Therefore, as with all chemical processes, it would be very desirable tobe able to reduce the cost of a thermo-chemical route to the pinacoloneor other ketones for use in the chemical industry on a commercial basis.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodfor the preparation of ketones from ketones and carboxylic acids so asto produce a high yield of the ketone while lowering the overall cost ofcapital investment and raw materials used in such a process. Anotherobject of the present invention is the providing of a recycling systemto provide high yields of wanted products at the expense of unwantedby-products.

It is a further object of the present invention to provide a catalystsystem for promoting such novel chemical reactions within the range ofcommercial utilization.

These and other objects of the present invention, and the advantagesthereof over the prior art forms, will become apparent to those skilledin the art from the detailed disclosure of the present invention as setforth hereinbelow.

A method has been found for the production of ketones comprising thesteps of: introducing a ketone and a carboxylic acid into a chamber;passing the mixture of the ketone and the carboxylic acid over a heatedcatalytically active material; and recovering the ketone.

It has also been found that unsymmetrical ketones can be produced by:mixing a ketone and a carboxylic acid; passing the mixture through acatalyst bed consisting essentially of a ceria-compound on an aluminasupport; and recovering the unsymmetrical ketone.

It has also been found that an unsymmetrical ketone may be produced by:mixing two different symmetrical ketones; passing the mixture through acatalyst bed consisting essentially of a ceria-compound on an aluminasupport; and recovering the unsymmetrical ketone.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In one important embodiment, unsymmetrical ketones may be producedaccording to the general reaction: (I) R₂ CO+2R'CO₂ H to yield2RR'CO+CO₂ +H₂ O wherein R is a hydrocarbon radical and R' is ahydrocarbon radical other than R. The acid reactant in the generalreaction (I) may be cyclic, acyclic or aromatic as well asmonocarboxylic or dicarboxylic. In the presently preferred embodiment,cyclic monocarboxylic acids are preferred. This reaction has been foundto occur over catalytically active materials with a relatively shortcontact time in a temperature range of 300° to 550° C. Unsymmetricalketones resulting from the above-cited reaction can be recovered inyields up to 80 percent or more. Groups representative of R and R' inthe above-cited starting materials would include aliphatic groups suchas methyl, ethyl, propyl, isopropyl, t-butyl, pentyl, hexyl, and benzyl,as well as aromatic substituents such as phenyl, p-tolyl and naphthyl.

In each specific case, conditions may need to be altered slightly tomaximize yields. For example, acetone and pivalic acid react over aceria-alumina catalyst at a temperature near 470° C. to producepinacolone. When using a two:one molar ratio of acetone:pivalic acidwith a ten second contact time, the conversion of the pivalic acid topinacolone was in the range of 80 percent of theoretical.

As another important feature of the present invention, most of theunconverted reactants in this novel chemistry can be recovered and refedinto the reactor zone to accomplish higher yields. For example, byrecycling the acetone and pivalic acid reactants above, virtually 100percent yields are possible. This results in about two moles ofpinacolone being produced per every one mole of acetone consumed.

It is thought that the above-described acetone and pivalic acid reactionto obtain pinacolone proceed as follows: ##STR1## It will be noticedthat two moles of the pivalic acid combine with one mole of the acetoneto provide two moles of pinacolone. Although not wanting to be bound toany particular theory, it is believed that the pivalic acid forms acomplex with the ceria-alumina catalyst system by losing the acidichydrogen atom off of the pivalic acid. Thereafter, the carbon to oxygendouble bond is attacked by the methylene anion of the acetone to providea shift of electrons to the oxygen atom and the loss of an oxygen atomwith the coupling of the acetone by its methyl group thereto. Thisresults in a probable intermediate of the formula (CH₃)₃ CCOCH₂ COCH₃.It is believed then that this intermediate is hydrolyzed causing acleavage which results in pinacolone and an acetic acid group leavingwhich will thereafter react with a second complexed pivalic acid groupto form more pinacolone. In this process, carbon dioxide and water arealso formed.

Further examples of ketones produced from ketones and carboxylic acidsinclude: acetone and benzoic acid to obtain acetophenone; acetone andpropionic acid to obtain methyl ethyl ketone and diethyl ketone; acetoneand phenylacetic acid to obtain phenylacetone; diethyl ketone and aceticacid to obtain acetone and methyl ethyl ketone; diethyl ketone andbenzoic acid to obtain propiophenone; benzophenone and acetic acid toobtain acetophenone; and benzoic acid and methyl ethyl ketone to obtainacetophenone and propiophenone.

Although the carboxylic acid reactant is preferred in reaction (I),carboxylic acid precursors have also been found to be useful. Forexample, it has been found that benzyl alcohol or benzaldehyde may besubstituted for benzoic acid in the reaction with acetone to obtainacetophenone. Further examples include, acetone and dimethyl succinateto obtain 2,5-hexandione; acetone and dimethyl terephthalate to obtainp-diacetylbenzene, and acetone and methyl pivalate to obtain pinacolone.Thus, carboxylic acid precursors include alcohols, esters, nitriles,anhydrides, aldehydes and alkyl ammonium salts having from one to threealkyl groups of one or two carbon atoms each. Mixtures of suchcarboxylic acid precursors including mixtures containing carboxylicacids as well as mixtures of carboxylic acids with themselves arecontemplated. Although not wanting to be bound to any particular theory,it is believed that reactions using the aldehyde or alcohol for astarting material proceed by an oxidation-reduction disproportionationof the feedstocks.

It has also been found that the present invention can be useful forrearrangements of ketones by themselves such as methyl ethyl ketonealone to obtain acetone and diethyl ketone and acetone and diethylketone to obtain methyl ethyl ketone.

This invention will be useful in reactions like: benzophenone andpivalic acid to obtain t-butyl phenyl ketone; 1,3-dichloroacetone andpivalic acid to obtain monochloropinacolone; and cyclopentanone andacetic acid to obtain 2,7-octanedione.

It is also contemplated that the present invention will provide goodactivity for other reactions falling within other general types, suchas: (III) RCH₃ +R¹ CO₂ H to yield RCH₂ COR¹, where R is an electionwithdrawing group such as 2 or 4 pyridyl and R¹ is alkyl or aryl.

Moreover, it is further contemplated that with yet additional reactants,good activity may be obtained for yet other reactions, while followingthe instant invention parameters, such as, for example: (IV) RCH₂ X+CH₃COCH₃ to yield RCH₂ CH₂ COCH₃ +HX, where R is an activating group suchas hydrogen, alkyl or aryl and X is a good leaving group such as ahalogen.

All of the above-cited reactions take place by passing the vapors of thereactants over heated catalytically active materials. Suitable materialsinclude iron filings, alumina, manganous oxides, thoria and ceria typesof catalysts. The preferred catalyst system, from experience, is a ceriacompound deposited on an alumina, silica or carbon support.

One specific catalyst is exemplified by a cerium acetate converted toceria on an alumina support and as such a good activity will be producedif the ceria concentration is in the range of 1 to 10 percent calculatedas CeO₂ to total weight. The amount used will depend upon the specificsurface area presented by the alumina support. Where the support used isalumina available from Harshaw Chemical Company under the trademark ofHarshaw Al 1404 T-1/8®, the specific area being approximately 190 squaremeters per gram, the range of ceria is preferably 5 to 10 percent. Aslight aging of the catalyst has been found during initial use, as isusual with such catalyst systems. Thereafter, this system will providegood activity of a steady nature for time periods in excess of 1000hours of use. The ceria-alumina catalyst provides a distinct practicaladvantage of thoria catalysts because the ceria is not radioactive, thuseliminating a hazard of thoria and the inconvenience of NuclearRegulatory Commission licensing and regulations covering its use. Otherspecific catalysts are discussed in greater detail hereinbelow inconnection with the examples.

This novel process of the instant invention will provide a distincteconomic advantage over prior methods, particularly for production ofpinacolone over either the mixed acid pyrolysis route or the formationof the mixed anhydrides and subsequent pyrolysis to the ketones. Lowercapital and operating costs are expected in the process of the presentinvention versus that of the mixed acid pyrolysis because the heat ofvaporization of acetone is less than that of acetic acid, thus requiringless energy. This is increased by the fact that one mole of acetone isequal to two moles of acetic acid used in the old methods. Further,about one-half as much carbon dioxide and water are produced, making iteasier to condense and recover the product and unreacted materials.There is also less dilution of the reaction mixture with by-productcarbon dioxide and water so that a reaction vessel only two-thirds tothree-quarters as large as that used in the acid pyrolysis route may beused to result in a savings in the cost of catalyst and reactor. Inaddition, smaller condensers with lower energy requirements will beadequate.

However, it should be understood that additives in minor amounts thatfind utility in catalytic reactions are contemplated for use with thereactants, for example, water used as a desorption agent may be used.

In order that those skilled in the art may more readily understand thepresent invention and certain preferred aspects by which it may bepracticed, the following specific examples are afforded to show themethods of preparation of various products.

EXAMPLE 1

An apparatus suitable for use in the above-described reactions wasassembled having a vertical tube furnace constructed over Pyrex tubingfor heating the reaction zone. The reaction tube contained a thermowellin the reaction zone to obtain accurate temperature readings. The uppersection was packed with glass beads where the reactants were heated upto reaction temperature while the lower section contained a smallerheating segment to sustain these temperatures. The preheater wasthermostatically controlled to provide more heat when reactants werebeing fed into the section to maintain the temperature. The catalystshould be positioned between the glass beads of the preheater and glassbeads near the outlet of the lower section so that it begins just belowupper section and runs down approxiamtely 75 percent of the length ofthe lower section and between the concentric thermowell and the glassthat contains the reactor. The reactor was connected by means of a "Y"tube to a condensate receiver on the bottom and two water-cooledcondensers in series on the vertically straight neck. For example, thelower condenser may be of a six-bulb Allihn type and the upper one ofthe Friedrich's type. Also, it might be desirable to use a feedreservoir on a triple beam balance connected to a metering pump to feedthe reactants to the system at a known rate. With a "Y" tube connectedto the upper section of the tube furance, the reactants may be fed intoone branch and a thermocouple well placed in the other branch formeasuring temperatures.

A thoria catalyst was prepared from 40 grams of thorium nitratetetrahydrate [Th(NO₃)₄. 4H₂ O] in water, impregnated on 200 ml. or 172grams of alumina available as Harshaw Alumina catalyst Al 1404 T-1/8®.The wetted alumina was stripped of water in a rotary evaporator underaspirator vacuum. This was transferred to a large porcelain dish whereit was heated strongly while aspirating the NO_(x) from it through awater trap. The resulting loose material was then placed into thereactor tube with glass beads ahead and behind the catalyst zone.

The system was then flushed out with acetone vapors to clear the systemof any residues and the catalyst temperature gradually rose to 440° to485° C. The feed reservoir was changed from acetone to a 2:1 molar ratioof acetone:pivalic acid. The condensate samples removed were composed of4 to 5 parts red organic layer over a colorless aqueous layer. Productpurification and gas chromatographic studies of the organic layer showedthe presence of pinacolone in yields ranging as high as 90 percent oftheoretical on a single pass. Recovery of reactants and recycling canachieve even higher yields.

EXAMPLE 2

A ceria catalyst was prepared from 100 grams of cerium acetate hydrate[CE(OAc)₃.XH₂ O)] and 400 ml. of water at room temperature withagitation to dissolve nearly all of the material. The solution wasfiltered and rinsed with several portions of water to result inapproximately 460 ml. of filtrate. The solution was then combined with1050 grams of Harshaw Alumina catalyst Al 1404 1/8®and tumbled in agallon jug. The solution was absorbed to leave no freely pourable liquidand thus wetting the alumina. The mixture was dried in a procelain dishat approximately 200° C. for 15 hours and then installed in theapparatus according to Example 1.

The system was flushed out according to Example 1 and the feed reservoircharged with a 2:1 molar ratio of acetone:pivalic acid. Pinacoloneproduct was recovered from the condensate in yields up to 90 percent oftheoretical as evidenced by gas chromatographic studies.

EXAMPLES 3-15

Using the apparatus of Example 1 and the catalyst of Example 2, otherreactions can be performed in a fashion similar to Examples 1 and 2. Ineach case, the reaction products were confirmed by mass spectra andquantitatively measured by gas chromatographic studies. These reactionsare summarized in the following Table 1. The Molar Ratio refers to theratio of the reactants in the order stated in the feed reservoir. Withthe exception of the pinacolone, no effort was made to maximize theyields.

                  TABLE I                                                         ______________________________________                                                           Reaction                                                   Ex.                Temp.    Molar %                                           No.  Reactants     °C.                                                                             Ratio Yield of Products                           ______________________________________                                        3    benzoic acid: 420-440  1:33  25 acetophenone                                  acetone                                                                  4    acetone:      430      1:1   38 methyl ethyl                                  propionic acid                 ketone                                                                      52 diethyl ketone                           5    acetone:dimethyl                                                                            470      3:1    2 2,5-hexandione                                succinate                                                                6    acetone:phenyl-                                                                             430-455  4:1   60 phenylacetone                                 acetic acid                                                              7    diethyl ketone:                                                                             420-440  1:1   40 acetone                                       acetic acid                  55 methyl ethyl                                                                 ketone                                    8    diethyl ketone:                                                                             430-480  4:1    8 propiophenone                                 benzoic acid                                                             9    benzophenone: 430-480  1:5    7 acetophenone                                  acetic acid                                                              10   benzoic acid: 450      1:4   21 acetophenone                                  methyl ethyl ketone          17 propiophenone                            11   methyl ethyl  400      --     6 acetone                                       ketone                       12 diethyl ketone                           12   acetone:diethyl                                                                             440-500  1:1   14 methyl ethyl                                  ketone                         ketone                                    13   acetone:dimethyl                                                                            440-460  40:1   2 p-diacetyl-                                   terephthalate                  benzene                                   14   acetone:      480-490  2:1   25 acetophenone                                  benzaldehyde                                                             15   acetone:benzyl                                                                              480-485  2:1:2  5 acetophenone                                  alcohol:water                                                            ______________________________________                                    

EXAMPLES 16-18

These examples show the use of alternative forms of the acid componentof pivalic acid are also suitable for producing pinacolone:

An apparatus suitable for use in the above-described reactions wasassembled having a vertical tube furnace for heating the reaction tube.The furnace was constructed around a pyrex reaction tube having a 2.5 cmO.D., a 2.2 cm I.D. and a length of 75 cm. The reaction tube contained aconcentric pyrex thermocouple well having a 0.8 cm O.D., the actualvolume of the reaction zone of the reaction tube being approximately 116ml. The reaction tube consisted of an upper section where the reactantsenter containing a preheater segment to bring the reactants up totemperature while the lower section contains a second heating segment tosustain these temperatures. The catalyst was positioned between glassbeads so that it occupied 38 cm of the center of the reaction tube withapproximately 18 cm of glass beads on each end of said tube. The reactorwas connectd to a condensate receiver under the reactor tube and thevapor rose through two efficient water-cooled condensers in series toensure that the reaction products were rinsed down into said receiver.This condensate receiver was a two-necked, 250 ml round bottom glassflask.

The catalyst was CeO₂ impregnated on alumina prepared from a filteredsaturated aqueous solution of cerium acetate containing a trace ofacetic acid deposited on Harshaw alumina Al 1404 T-1/8® and oven driedat 100° C. overnight. The resulting loose material was then placed intothe reactor tube (occupying approxiamtely 38 cm in the center of thetube) with glass beads on each end (occupying approxiamtely 18 cm oneach end of said tube) resulting in approximately 3 percent by weightCeO₂ being present in the reaction tube.

The system was flushed with acetone by feeding acetone at a rate of oneml per minute (ml/min) using a metering pump. The preheating zone wasgradually brought to 470° C. and the reaction zone gradually brought to475° C. by the use of variacs. The feed was changed from acetone to thevarious reactants at the molar ratios set out in Table II below. Thecondensate product samples were collected in the condensate reservoirand analyzed using gas chromatography and gas chromatography/massspectroscopy to prove the identity of the products.

The system was not optimized for each reaction and, therefore, yieldswere not determined; however, yields of approximately ninety percent orhigher should be possible with proper optimization.

                  TABLE II                                                        ______________________________________                                                             Reaction                                                 Ex.                  Tempera-  Molar                                          No.  Reactants       ture (°C.)                                                                       Ratio Product                                  ______________________________________                                        16   Methyl pivalate:acetone                                                                       475       1:2.05                                                                              Pinacolone                               17   Pivalonitrile:acetone                                                                         475       1:1.46                                                                              Pinacolone                               18   Trimethylammonium                                                                             475       1:3.75                                                                              Pinacolone                                    pivalate:acetone                                                         ______________________________________                                    

EXAMPLE 19

This example shows that other acids may be used in place of pivalic acidin this novel chemistry.

Using the apparatus, catalyst and method of Examples 16-18, cyclohexanecarboxylic acid and acetone in a molar ratio of 1:2.76 was introducedinto the system after purging with acetone. Methyl cyclohexyl ketone wasproduced and identified as in Examples 16-18.

EXAMPLE 20

This example illustrates the applicability of using non-pivalic acid,acid precursors.

Again using the apparatus, catalyst and methods of Examples 16-18,acetonitrile and diethyl ketone in a 1:1 molar ratio were introducedinto the system after purging with acetone. Methyl ethyl ketone wasproduced and identified as in Examples 16-18.

EXAMPLE 21

This example illustrates the applicability of recycling a mixture ofproduct and unreacted starting materials to increase the product yield.

Using the apparatus, catalyst and method of Examples 16-18, acetone anddiethyl ketone in approximately 1:1 molar ratio were introduced into thesystem. Three distillation cuts of the reaction product were isolated.The second cut contained mostly the methyl ethyl ketone product. Thefirst cut being from 25° C. to 70° C. and containing mostly unreactedacetone and the third cut being above 86° C. and containing mostlyunreacted diethyl ketone. These two cuts were combined and gaschromatographic analysis revealed 1.4 percent methyl ethyl ketone. Thiscombined material was thus recycled through the apparatus and collectedas described above. Gas chromatographic analysis revealed a methyl ethylketone yield of 2.8 percent.

The following examples illustrate the use of various suitable catalystsand catalyst supports.

EXAMPLE 22

A ceria catalyst was prepared from 21.5 g of cerium chloride hydrate(CeCl₃.7H₂ O) and approximately 60 ml of water at room temperature withagitation to dissolve the cerium compound. To this solution 48.8 g of6-14 mesh coconut charcoal was added and this mixture placed in a rotaryevaporator. After evaporation of most of the liquid with repeatedapplication and release of vacuum, the moist charcoal was driedovernight in an oven at 120° C. and then installed in the apparatus ofExample I as disclosed in Example I.

The system was flushed out according to Example I and the feed reservoircharged with a 2:1 molar ratio of acetone:pivalic acid. Pinacoloneproduct was recovered from the condensate as evidenced by gaschromatographic analysis.

EXAMPLE 23

A magnesia catalyst was prepared using 40.0 g of MgO dissolved inapproximately 40 ml of water containing 14 g of acetic acid andimpregnated onto 75 g of alumina (Harshaw Alumina Al 1404-T1/8 ")following the procedure of Example 22.

The system was flushed out according to Example I and the feed reservoircharged with a 2:1 molar ratio of acetone:pivalic acid. Pinacoloneproduct was recovered from the condensate as evidenced by gaschromatographic analysis.

EXAMPLE 24

An iron oxide catalyst was prepared from 25.8 g of FeCl₃ and 85 ml ofwarm water with agitation to dissolve nearly all of the material. Thesolution was then impregnated onto 114 g of Harshaw Al 1404-18®following the procedure of Example 22. This material was dried in aporcelain dish overnight at 400° C. and then installed in the apparatusaccording to Example 1.

The system was flushed out according to Example I and the feed reservoircharged with a 2:1 molar ratio of acetone:pivalic acid. Pinacoloneproduct was recovered from the condensate as evidenced by gaschromatographic analysis.

EXAMPLE 25

Using the method and apparatus of Example 1, pinacolone was producedfrom a 2:1 molar ratio of acetone:pivalic acid using a commerciallyavailable zirconia catalyst. This catalyst is sold as Harshaw Zr0304-T-1/8 " catalyst and contains 98 percent zirconia and 2 percentalumina and has a surface area of 50 m² /g. Production of pinacolone wasconfirmed by gas chromatography.

EXAMPLE 26

Using the method and apparatus of Example 1, pinacolone was producedfrom a 0.6:1 molar ratio of acetone:pivalic acid using a commerciallyavailable chromia catalyst. This catalyst is sold as Harshaw Cr0304-T-1/8®" catalyst having a surface area of 120 m² /g. Production ofpinacolone was confirmed by gas chromatography.

Thus, it should be readily apparent from the foregoing description ofthe preferred embodiments that the method hereinabove describedaccomplishes the objects of the invention and solves the problemsattendant to the method of preparation of ketones.

What is claimed is:
 1. A method for the production of product ketonescomprising: introducing a reactant ketone and a carboxylic acid and/orcarboxylic acid precursor into a chamber; passing the mixture of saidreactant ketone and carboxylic acid and/or carboxylic acid precursorover a heated catalytically active metal oxide material; and recoveringthe product ketone.
 2. A method according to claim 1 wherein thecatalytically active metal oxide material is selected from the groupconsisting of oxides of cerium, thorium, iron, magnesium, chromium,zirconium and tungsten, preferably a ceria compound, on a support.
 3. Amethod according to claim 2 wherein the support is alumina.
 4. A methodaccording to claim 1 wherein the temperature of reaction is in the rangeof 300° to 550° C.
 5. A method according to claim 1 wherein the reactioncontact time of the reactants and the catalytically active material isin the range of 0 to 60 seconds.
 6. A method according to claim 1wherein the ketone is acetone and the carboxylic acid is pivalic acid toyield pinacolone.
 7. A method according to claim 1 wherein the ketone isacetone and the carboxylic acid is benzoic acid to yield acetophenone.8. A method according to claim 1 wherein the ketone is acetone and thecarboxylic acid is propionic acid to yield methyl ethyl ketone anddiethyl ketone.
 9. A method according to claim 1 wherein the ketone isacetone and the carboxylic acid precursor is dimethyl succinate to yield2,5-hexanedione.
 10. A method according to claim 1 wherein the ketone isacetone and the carboxylic acid is phenylacetic acid to yieldphenylacetone.
 11. A method according to claim 1 wherein the ketone isdiethyl ketone and the carboxylic acid is acetic acid to yield methylethyl ketone.
 12. A method according to claim 1 wherein the ketone isdiethyl ketone and the carboxylic acid is benzoic acid to yieldpropiophenone.
 13. A method according to claim 1 wherein the ketone isbenzophenone and the carboxylic acid is acetic acid to yieldacetophenone.
 14. A method according to claim 1 wherein the ketone isacetone and the carboxylic acid precursor is dimethyl terephthalate toyield p-diacetylbenzene.
 15. A method according to claim 1 wherein theketone is acetone and the carboxylic acid precursor is selected from thegroup consisting of benzyl alcohol and benzaldehyde to yieldacetophenone.
 16. A method according to claim 1 wherein the ketone isacetone and the carboxylic acid precursor is methyl pivalate to yieldpinacolone.
 17. A method for the production of unsymmetrical ketones ofthe formula RR'CO where R is a hydrocarbon radical and R' is ahydrocarbon radical different from that of R comprising: introducing aketone and a carboxylic acid and/or carboxylic acid precursor into achamber; passing the mixture of said ketone and carboxylic acid and/orcarboxylic acid precursor over a heated catalytically active metal oxidematerial; and recovering the unsymmetrical ketone.
 18. A method asclaimed in claims 1 or 17 wherein the reaction products are recycledthrough a catalyst bed, thereby improving the yield of the desiredketone or ketones.